The present invention relates to medical diagnostic and screening systems and methods. In particular, the present invention relates to non-invasive cardiac imaging and functional analysis systems and methods.
While cardiac imaging and functional analysis is the largest single nuclear medical imaging application, there remains a tremendous unmet need for improved cardiac imaging and functional analysis systems and methods. This need is exemplified by the fact that historically, for 30%-50% of those stricken with coronary artery (occlusive) disease (CAD), the first symptom of the disease is death. This has motivated considerable effort to develop diagnostic methods and apparatus to detect CAD prior to the onset of fatal symptoms and assist in the development and implementation of preventive measures.
Two strategies are presently used to reduce morbidity and mortality from CAD. The first involves screening for modifiable cardiac risk factors, such as hypertension, elevated serum cholesterol, cigarette smoking, physical inactivity, and diet. The second involves early detection of CAD. The principal tests for detecting CAD include resting and exercise ECGs, which can reveal the presence of myocardial infarctions and inducible myocardial ischemia. Tc-99m myocardial perfusion and computed tomography (CT) calcification scoring can provide visual evidence of plaques in the coronary arteries. Thallium-201 scintigraphy, exercise echocardiography, and ambulatory ECG (Holter monitoring) are less commonly used for screening purposes. None of these strategies has produced a solution to the high incidence of death due to undetected CAD. Accordingly, there remains an unsatisfied need for improved cardiac imaging and functional analysis systems and methods for reducing morbidity and mortality from CAD.
The following presents a simplified summary of the invention in order to provide a basic understanding of some of its aspects. This summary is not an extensive overview of the invention and is intended neither to identify key or critical elements of the invention nor to delineate its scope. The primary purpose of this summary is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.
One aspect of the present invention relates to a method of screening patients for an early stage of CAD. According to this method, a patient is screened based on the time-activity curve for a radioactive tracer passing through a left ventricle region of the patient""s body. The time-activity curve can be analyzed by comparing it to a time-activity curve for a region of the patient""s body downstream of the left ventricle, such as the patient""s ascending aorta or the patient""s brain. A quick transit through the patient""s left ventricle region indicates an early stage of CAD wherein the free volume of the patient""s coronary artery system is reduced, but the patient does not necessarily yet suffer from inducible myocardial ischemia.
Another aspect of the present invention relates to a method for obtaining a time-activity curve for a radioactive tracer passing through a left ventricle region of the patient""s body. According to this method, an array of gamma particle detectors is employed to obtain data for a region of interest which is larger than and encompasses a left ventricle region of the patient""s body. An analysis of data from the detector array identifies the subset of detection data that corresponds to the left ventricle region. This method avoids difficulties associated with accurately locating the left ventricle region prior to a testing or screening procedure.
A further aspect of the present invention relates to another method for obtaining a time-activity curve for a radioactive tracer passing through a left ventricle region of the patient""s body. According to this method, a second technique, such as ultrasound, MRI, x-ray, computed tomography (CT), planar nuclear medicine, positron emission spectroscopy (PET), single photon emission computed tomography (SPECT), or a second radioactive tracer, is employed to locate the left ventricle region. A time activity curve is then obtained using a gamma particle detector or detector array positioned according to the determined location of the left ventricle region. Potential errors resulting from failure to accurately locate the left ventricle region are thereby avoided.
A still further aspect of the present invention relates to a method of obtaining images of a patient""s heart. According to this method, the images are obtained with a high temporal resolution gamma camera. A high temporal resolution gamma camera provides diagnostically meaningful images of the patient""s heart even when the high temporal resolution comes at the expense of spatial resolution. Imaging is further improved with the use of a second gamma camera at an angle to the first gamma camera. Two gamma cameras can be used to provide three-dimensional structural information, measure heart motion in three dimensions, and be used to correct for bulk movements of the patient motion in three dimensions.
Other advantages and novel features of the invention will become apparent from the following detailed description of the invention and the accompanying drawings. The detailed description and drawings provide certain illustrative examples of the invention. These examples are indicative of but a few of the various ways in which the principles of the invention can be employed.